Apparatus for parallax correction



-7, 47. R. C. KNOWLES ETAL 2,428,372

APPARATUS FOR PARALLAX CORRECTION Filed March 1, 1945 5 Sheets-Sheet 1 CGkREC TE 0 GUN POSITION l/NcaRREcTEo GUN P051 T/o/V r O 25,70 Az/Muw/ AX/s Z INVENTORS five/MR0 c. Kwanzaa #525527 #4 may Y /Y W 3 Sheets-Sheet 3 INVENTORS HARD C./(/VOWLES #[RBERT F/ARR/, 0/2. WWW

R. C. KNOWLES ETAL APPARATUS FOR PARALLAX CORRECTION Filed March 1, 1943 sigma/u o4 byluwsnlvai 9, y

Oct. 7, 1947.

Quay/u. 02 (ZZLL/WSNVALL -?J Patented Oct. 7, I947 UNITED STATES PATENT OFFICE APPARATUS FOR PARALLAX CORRECTION Application March 1, 1943, Serial No. 477,666

Claims. (01. 235--61.5)

This invention relates, in general, to a method and apparatus for correcting gun aiming angles due to the spacing of the gun station from a control or sighting station. It is particularly dirooted to parallax correction in inter-aircraft fire control systems.

Increases in the size of aircraft have increased the number of gun positions carried by the craft, as well as increasing the size and range of the guns. These factors have made it desirable to obtain greater accuracy from the guns by increasing the accuracy of the fire control system. With the increase in the number cf gun positions it was found desirable to have one or more central fire control stations for aiming all or any portion of the guns on the craft at selected targets.

The high velocities involved in the prediction computations necessary for inter-aircraft fire control systems have made it further desirable to correct for errors heretofore considered as insignificant. The accuracy of inter-aircraft fire control systems has reac ed the point Where the off-set of gun stations relative to the fire control stations has become an important factor and is becoming more important as the size of aircraft increases.

Therefore, the present invention contemplates a fire control system having several gun positions, any one or more of which may be controlled by one or more central control stations.

In the past, fire control systems have been divided mainly into two groups; that is, those for use on land, and those for use aboard naval craft. In both of these systems parallax corrections have been effected. However, the corrections necessary for the high accuracy required in intor-aircraft fire control systems necessitate more accurate and comprehensive parallax correc tions. Thus, the present invention includes a parallax correction in which factors hereto ore considered unimportant have been included to obtain more accurate fire from the aircraft.

The development of fire control systems for use on land has included parallax correction apparatus in which the data has been corrected periodically by manual adjustment, and in some cases, in which continuous adjustments have been made for a portion of the parallax correction. Such continuous adjustments usually include the azimuth parallax correction which varies the angle of train of guns in azimuth due to the spacing between the sight or control station and the gun station. Such systems, however, neglected the elevation parallax correcti n,

because usually the range of the guns was comparatively long and the difference in the range due to the positioning of the two stations was negligible relative to the range.

Some land base fire control systems, such as those used for anti-aircraft fire, operate on a plan prediction system in which the computing and predicting mechanisms operate in rectangular coordinates. For such systems it is pos sible to effect a parallax correction by introduc ing three constant linear distances representing three components of the distance between the two stations and corresponding to the rectangular coordinate components used in the mechanism.

In some respects, fire control systems on naval craft are similar to those on aircraft, in that, the computing mechanism must consider movements of the craft, as well as movements of a target. In most naval fire control systems a continuous adjustment is made to correct for azimuth parallax. However, this is not a particularly difficult correction because the control station, as well as each of the gun stations, is usually considered to be positioned on a reference line running longitudinally of the craft, This may be referred to as the zero azimuth line, and hence it is only necessary to compute the difference in the angle of train relative to the zero azimuth line for different points along the line.

Furthermore, naval fire control systems have only corrected for elevation parallax due to the difference in height between the guns and the sighting or control station which may be located in the super-structure of the ship. Corrections for changes in elevation due to the difference in range of a target from the control station and the gun station are usually neglected for the same reason as they are neglected on a land base fire control system, namely, that the difference in range is comparatively small with respect to the total range, and also that the elevation correction is comparatively small. Another reason for neglecting this correction is that the target is usually in the same horizontal plane as the firing craft and, therefore, the elevation angle is usually a minimum and is dependent solely upon range, whereas in inter-aircraft fire the targets may be located in different horizontal planes and. the elevation angle is dependent upon the relative positions of the target and the gun, as well as upon the range of the target.

For several reasons parallax correction mechanisms for inter-aircraft fire control systems are complicated, One reason for this is that the varus gun turrets and sighting or control stations e not necessarily arranged on a common refence line, since it is customary to position some ms, at least, in the wings of the craft as well in the fuselage.

Another reason for the complication of the cor- :cting mechanism is that. the ranges are shorter-.- id the elevation aiming angleofthegurris=deandent upon the elevation of a target relative v the gun as well as upon the range of the tar.- at. As the difference in elevation-betweenthe. irget and the gun increases, the elevation in ie angle of the gun increases. With range. herefore, it is necessary to'include-inathe, paral- LX correction mechanism an elevation parallax. orrection due to the difference in range-of airget relative to a sightingaor. control station, nd relative to the gun station or turret.

One factor which simplifies inter-aircraftpar llax correction as compared with some naval nd land.installationsziszthat all of the gunsaandi ontrol stationsmay'be. considered :to lie in the ame plane, namely,' the. plane-.ofthe-aircraft. llthough there may hesome; difference in"; the [eight of, these stations, this is comparatively mall andmay be. neglected forrpresent considrations: Thus,the"parallax:correctionscontemdated hereint are-due; to-the distance: separating: t. gun; from. a: control station on Sight; measured: n: the .plane; of the aircraft.

One. object of:the'inventionv is to provide an; Lpparatus for parallax correction: including eleation. parallaxscorrectmn due I to, 1 the 1 difference nxrange of a target ,fromtwoseparated stations.

Another object of the invention is to provide.- in"; apparatus for parallax. correction in which ;he. correction-.may; becomputed for any position; )ftheyariousstations; relative :to the longitudinal axis-:or reference: liner-of the, craft.

Anfurther objectfofztherinventioniis to provide continuousazimuth: and: elevation parallax correctionsrto determine: the aiming; angle :f or a a re motely positioned. gun from: azimuth, elevation. and range. data of; a. target relative; to :asighting; or'control station;

Further obj ects;v and-r advantages:;of: the .inven tion: will become apparentx-frointhe: following; specifi'cation and accompanyingrdrawings; wherein:

Fig. 1 is aplan view:of:an:.aircrait;showing the relative positionofisightmgistationszand: gun turrets.

Fig; 2 is-za space diagram showing theposi-tion o-f atarget. relative .to. one; sighting-:station and. one gun: turret On the; craft:

Fig. 3 i is a" schematicillustration of a aparallax correctionimechanism embodying the invention and in which .some. parts-are in section and othersare broken away i for purposes of elearness.

Fig. i is a section taken on the; line 1- of Fig. 32

Fig. 5 is'a.schematic'perspectiveview of another parallax correction mechanism embodyingthe' invention.

Referringfirstto Fig; 1; an aircraft, designated generallyat-i, is illustrated as lyingxin 'a horizontal plane. Since the plane of the craft is'normally horizontal, present orientation data is measured and computed'relative to this plane; The-zero azimuthreference'line maysbe' considered the longitudinalaxis 2" of theicraftand, for purposes of the following description, will be considered as thezero'line with allazimuth angles being measured clockwise from thenose ofthe plane; as it appears in Fig. 1. It shouldbe-llridlstood that this definition of the zero azimuth line is merely one of convenience for purposes of description of the present invention, and should not be considered in a limiting sense, as any line may be used for a zero azimuth reference.

The craft includes two sighting or control stations3 andi l in; the nose; and-tail? of the plane, respectively, which happen to -be-locat'ed" on the zero azimuth line. However, this again is a mat- I'. ter of convenience, as the gun or sighting stations .may.be..located.in.the wings of the craft or elsewhere at points off-set relative to the longitudinaljaxis,.2. Ifzthe control stations 3 and G are offeset, theazerorazimuth line for these stations i is likewisezoff-set so' it will pass through them.

Thecraft shown in Fig. 1 has an upper turret 5 inthe-fuselageand a lower turret (not shown) which is also located in the fuselage and may be directly-below the upper turret 5. A pair of wing turrets 9 and II are carried by the respective wings' of the craft. Gthergun turretsmay'be provided at; various positions. on the: craft' such as other portionsiof the-wingseor; the-tail. However,:those. turrets shown-will. sufiice for a descriptionof the. parallax-correction with: which; the present invention is concerned;

Eitherof-sthe control. stations-.3.- or-&4. may. controlralliof the guns, or*the.-.control.of=the guns: may be divided betweenthe twoicontrol stations.

Eachof the control stationszineludes-a compute ing; mechanism which is suppliedwith.orientationi data .froina ,sighting; device -.and: utilizes this data to predict: the fHtUIB-POSitl-OH ot. a: target depending, upon: its direction and velocity. After the; prediction hasxbeenx computed, theacomput'er determineszangles at: which gunsshould be: aimed to direct projectiles to the point at which they. will? intercept: a target; Thisypoint is: defined? as the: futurezposition ofathe-ytarget. The. gun aim. ingianglesthusrdetermined;apply to a:gun located.- atsthe sighting'or computing station. In: order. to -correct; these; angles: for: remotely positioned guns; the: parallax. method: and apparatus describedherein wasdeveloped.

.1 Flor theifuselage ;turr.et: 5-, whichzis located.v on thezlongitudin'al axiszz, the;az-imutlrriparallaxrcor= rection is quite similar to that previouslyzencoune tered in .navalifires control: systems;'sinc.e thezcorrectionidepends solely:'uponztheeanglethat a line of: sight. makesriwith alinegbetweenithe: sighting and gun stations 'which: iscoincident with the longitudinal. axis: 2: For-;-the wing turrets: 9 and l I ;,the.1ine 'betweenitherscontrolistation? and the guns. iscdisposed at an angie;tothe longitudinal axis-.2: Therefore; it isnecessary-"to includezthis angle: at; the line. connecting: two: stations with the longitudinal" axis. in azimuth parallax core rectioncomputations: For-boththefuselage and wingfturrets itris necessary toiinclude-the. elevation parallax zcorrectionrduezto changes. in range, as'will subsequently appear:-

Fig:. 2*.is 'a space diagram= showing:theposition of a target T" such asithezaircraftzlii'." The-cone trolrstation. or, computer-"Grandgun station or turret G; selectedfor' this diagram, corresponds to the control station. 3. and gun ll' on the air= craft l shownin Fig.- 1'. Fromexamination of this diagram, itwill be'apparent that'the'orientation angles of'the target-T'Telative to the computer Care considerably difierentrfrom the ori-' entation angles. of the targetfT-relativa tothe gun turret G. The'computer (landrturret Gare both considered. to liein the: plane of the craft; that is the azimuth-plane; and thecomputer C .is further considered. to" be positioned on the zero azimuth axis which, in the present case, is coincident with the longitudinal axis of the craft. The line connecting the computer C with the turretG also lies in the azimuth plane.

- The distance D from the target to the computer corresponds to the slant range of the target and D represents the slant range of the target relative to the gun turret G. The point TA represents the projection of the target T to the azimuth plane, and the lines R and R represent the horizontal range (the range in the azimuth plane) of the target relative to the computer C and gun turret G, respectively. The azimuth and elevation angles of the targetrelative to the computer C are designated AG and EG, respectively, since the angles with which the parallax correction mechanism is concerned'are gun' aiming angles for directing guns from the point C toward the predicted future position of the target.

Although Fig. 2 shows lines connecting the computer and turret with the target, these lines should be considered as lines to the future position of the target. That is, the craft l3 should be considered as the future position of the target. The gun aiming angles relative to the turret G are designated by A's and EG for azimuth and elevation, respectively.

It will be apparent from Fig. 2 that the azimuth parallax correction angle 6A is equal to the difference between the azimuth angle of the target relative to the gun turret and the azimuth angle of the target relative to the computer AG. Similarly, the elevation parallax correction eE is equal to the difference between the elevation angle of the target relative to the gun turret E's and the elevation of the target relative to the computer Es. These relations may be expressed by the following equations:

Fro'mthe trigonometric. relations of these angles it may be shown that S Sill (AG) and that D sin E 1 /R +S -2S-R cos (oz-A From Fig. 2 it may be seen that R=D cos Ea (5) By substituting for the value of R in Equation 44, it follows that S sin (aAg) q sin" 63 E r-tan D sln EG Equations 6 and 7 may be written as It has been determined empirically that all but the first expression in the series of the above equations may be eliminated, and further that the azimuth and elevation parallax corrections are sufficiently small that the angles (measured in mils) Thus, the azimuth and elevation parallax corrections may be approximated as S sin (aA D cos E (10) and 6E=S Sin EG'COS (QC-AG) From the foregoing equations it is apparent that the azimuth parallax correction EA varies in accordance with the horizontal range R; the angle (or-Ac) defined by the line representing the horizontal range R and the line connecting the control station C and the gun turret G and the distance S between the control station and the gun turret. Similarly, the elevationparallaxcor- V rection eE varies in accordance with the slant range D; the angle (ocAG) defined by the line representing the horizontal range R and the line connecting the control station 0 to the gun turret G; the elevation of the target EG; and the distance S between the two stations.

Since Equations 10 and 11 represent solutions for the desired azimuth and elevation parallax correction angles, and since these angles are expressed in terms of quantities available at the computer, it is possible to determine parallax correction angles by suitable mechanisms for solving these equations. One such mechanism which may be used to solve the equations is shown schematically in Fig. 3.

As previously stated, a computer in the fire control system determines the azimuth and elevation gun aiming angles AG and EG- with respect to the control station C. The data thus computed is used to position shaft 2i in accordance with the gun azimuth at the computer and shaft 22 in accordance with the gun elevation at the computer. The range of the target is also determined at the computer and this data may be used to position shaft 23. It should be understood that this parallax correction mechanism is intended for use with a computer that continuously computes target orientaion data and gun aiming angles. Therefore, the shafts 2|, 22 and 23 will be continuously positioned in accordance with the azimuth, elevation and range calculated by the computer.

Shaft 2| rotates a pinion 24 that meshes with a gear 25 to drive the azimuth data into a differential 26. The other input of this differential 26, as represented by shaft 21, is positioned in accordance with the angle between the longitudinal reference line (zero azimuth line) of the craft and the line connecting the control station C with the gun station G, that is, the angle 0:. This shaft is rotated an amount corresponding to the angle a by a gear '28 that is driven from a rack 29, the rack being positioned by a solenoid 3! in one of two positions, thus providing for introducing either of two separate values of a where the mechanism is used for guns in different positions on the aircraft. By varying the limits of the translation of the rack 29, the values of a may be adjusted for any given installation. The inputs to the differential 26 are arranged in such a man- ,may be considered equivalent to their sines. ner that the difference between the angle a and reciprocal ofthe slant range 7. the gun .azimuthAeswilI: appear on. the output gear 33. Thus, thegear 33 is continuously positioned in accordance with the angle (lZ-AG) between the line representing horizontal range R and the line connecting the two stations. Rotation of gear 33 drives through gear 34, shaft 35 and bevel gears 36 and 31 to position a shaft 38 in accordance with the angle (AG) The shaft 38 also positions a pinion 39 in accordance with this angle. Pinion 3-9 drives one disc it-of a component resolving mechanism 4| that positions a slot 42 in the disc 40 in accordance with the angle (Qt-AG) The outer disc 43 of the resolving mechanism M is positioned in accordance with a of the target in a manner to be described.

The shaft 23 that is positioned in accordance with the slantrangeD drives through bevel gears 44 and 45 to rotate a shaft 46 carrying a cam 47. The surface of the .cam l'l. is so designed that a follower 48 riding thereon will be positioned. in accordance with thereciprocal' of the range as. the shaft rotates in accordance with the slant range D. This follower translates a rack 49 that meshes with a pinion 5| to drive through a shaft 52, bevel gears 53 and 54 to position an input shaft 55 of a, differential 56 in accordance with the reciprocal of the. range Thisreciprocalloi the range is driven through the differential to the output gear 57, which positions an idler gear 58 to drive the lower disc 43 of resolving mechanism in accordance with the'reciprocalof the slant range this block 63 will be positioned in accordance with the same quantity.

The purpose of the differential '56 isto avoid movements of the upper disc from causing movement of the block 63 in the slot 42 which would occur due to the fact that the rack moves with the upper disc and meshes with the pinion 6!, which might be held relatively stationary. The differential 56 accomplishes this by meshing input gear 65 with the upp'er'disc 40 thereby driving the lower disc 43 an amount corresponding to all movements of the upper disc. Hence, the pinion GI and rack 62 will rotate as a unit and only when the shaft 52 drives a change in the range into the differential 56 will the block 63 be moved relatively to the upper disc 40.

A pair of racks 'II' and I2 are arranged to slide in horizontal and vertical guides (not shown) re- 8-. spectivelyx. The rack TIT carriesiran:arm.'.l3s has .a slot 1.4 formed therein and adapted atoms-- ceiVe: a pin. I5 thatris'carried'.by-tlreblocklfl. It; will be apparent that movements. of the. pin. :15 due.- to movement of' either onexorbotn; of the discs 48- and; 43 will causehorizontal movementof' the rack I I. and arm;'I:3.

Similarly, the vertical rack.- :12: has? an arm'l'l formed with a slot. 1&alsoadapted toreceive'; the pins- I5, whereby movement of the block'63l'wi-l-l cause. vertical movements: of the; rack; 1.2:.

By reference to Fig; 3;. it will. be seerrthat'slot 42' is positioned by the. disc. 4.0"at.anrangletothe vertical equal tothe angle (:a-A-G1).=. Sineethe. block 63 is translated along: slot 42 an amount equalto the reciprocal of therslant-range the racks II and I2 are respectively translated by amounts corresponding to the; horizontal. and vertical co-mponentsof this reciprocal. which may be expressed in terms of sine and cosine of the angle xAG)1,, respectively. Thus, the. rack 1.1 is translated an amount. corresponding. to the. expression sin (a A0) D and the rack 1-2 is translated an amount corresponding to The rack II meshes with. aqgear 8lfthat drives. through shaft 82;. bevel gears: 83 and. 84. to position a shaft 85' and pinion 86. in: accordancewith the expression sin (d- A Similarly, the rack' I2 drives through a pinion I45, shaft I46 and bevel; gears: I 41 and M8 to position a shaft I49 and pinion: I50 in accordance with the expression cos (a-A'G) D It will be apparent that at any time these quantities may bev changed for different turrets by merely causing the solenoid 3| to adjust shaft 27 in accordance with: a difieren-tangle a. This will automatically adjust pinions 86 and 93 to provide the corresponding data for the differen turrets.

The pinion 86 meshes with axrack' 8'11 totranslate a three-dimensional cam 88 that is rotated by an elongated pinion 89 on shaft 22. Thus, the cam 88 is translated in accordance: with the expression sin (a.A D,

and is rotatedv in accordance; with. the gun elevation, since the shaft 22 is connected to the computer for obtaining this data. The-surface. of. the. cam St is laid out in a manner'suchthat it will multiply the input from pinion 86 by the reciprocal of the cosine of the elevation angle and thus translate a follower 89 riding on the surface of the cam. an amount proportional to. the expression sin (a A D cosE Thus, the follower 83has computed the azi' muth parallax correction 6A- with the exception of the multiplication by the distance S between the sighting station or computer and the gun station or turret G. This multiplication is effected in a manner now to be described.

The follower 89 carries a rack 9| that meshes with a pinion 92 on shaft 93 which drives through bevel gears 94 and 95, shaft 96 and bevel gears 91 and 98 to rotate a shaft 99 in accordance with the foregoing expression. Shaft 99 is arranged to alternatively drive through a clutch IOI or a clutch I02 to rotate either pinion I03 or pinion I04. These clutches are controlled through translation of a sleeve I06 on the shaft 99 by a lever I01 pivoted at I08 that engages a collar I09 on the sleeve I06. The position of the lever I01 is adjusted by a solenoid at III which moves core II2 to close either clutch IN or I02.

7 As shown in the drawings, clutch IOI is closed and the shaft 99 is driving through pinion I 03 to drive gear II 3. The ratio of the pinion I03 to gear H3 is chosen to be proportional to the distance S between the sighting station and the gun turret. Thus, the gear I I3 is positioned in accordance with the expression sin (a-A D cos E;

to obtain the azimuth parallax correction angle EA in accordance with Equation 10.

When the core II2 of the solenoid III is in its other position, link I01 opens clutch IOI and closes clutch I02, whereby shaft 99 drives through pinion I04 to position gear H5 in accordance with the azimuth parallax angle 6A for a different value of S. The gears H3 and H5 are integral and are arranged to drive the azimuth parallax correction angle into a differential H6. The other input to the differential is driven by the shaft 2I. Thus, the differential I I6 adds the gun azimuth AG at the computer to the azimuth parallax correction angle eA to obtain the gun azimuth angle A'G at a selected turret by rotating output gear H1 in accordance with that angle A'o. Thus, output gear II1 meshes with a suitable gear IIB to drive a shaft H9 in accordance with the gun azimuth angle A'c at the selected turret. A suitable data transmission and servo system may be controlled by the position of shaft I I9 to position guns at the remote turret in azimuth corresponding to the angle Ae.

The elongated pinion 89 also rotates a threedimensional cam I2I in accordance with the gun elevation angle at the computer by rotating a gear I22 on the cam. The cam I2I is translated by a rack I23 that meshes with the pinion I50 whereby the cam I2I is translated in accordance with the expression cos (a A0) The surface of the cam I2I is laid out in a manner such that the expression by which the cam is translated will be multiplied by the sine of the gun elevation angle Ed and a follower I24 riding on the surface of the cam will be translated an amount corresponding to the expression sin E cos (or-Ag) The follower I24 carries a rack I25 that meshes with a pinion I26 to drive a. shaft I 21 in accordance with the foregoing expression. The shaft I21 operates through clutches I28 and I29 to drive pinions I3I and I32. The clutches I28 and I29 are actuated by the solenoid III through link I33 pivoted at I34, which engages a collar I35 to alternatively open and close the two clutches in a manner similar to that described in connection with clutches I M and I02. The ratio of pinion I3I to gear I36 is the same as the ratio of pinion I03 to gear I I 3, that is, a value proportional to the distance S, between any two stations. The ratio of the pinion I32 to gear I38 is proportional to a similar distance S for two other stations and is equal to the ratio of the pinion I04 to the gear I I5.

The shaft I21 drives through clutch I28 to rotate gear I36 in accordance with the elevation parallax correction angle as determined by Equation 11. Gears I36 and I38 are integral and represent one input to a differential I4I, the other input of which is driven by the shaft 22 in accordance with the gun elevation angle EG at the computer. The diiferential I4I adds the gun elevation angle Ea at the computer and the elevation parallax correction angle eE to position output gear I42 in accordance with the gun elevation angle EG at the turret. The gear I42 drives a gear I43 to position shaft I44 in accordance with the gun elevation angle at the turret. Shaft I44 may be connected through suitable data transmission and servo mechanisms to position the elevation angle of the gun EG at the remote turret.

In the mechanism just described, provision is made for introducing two values of the angle or of the line connecting a turret and sighting station relative to the azimuth reference line. Also, provision is made for introducing two values of the distance S between a turret and sighting or control station. It should be understood that suitable mechanism for introducing more than two values of a and S may be provided without departing from the invention.

The provision for changing the values of a and S makes the use of this mechanism flexible. It is readily adaptable for use with one turret and more than one computer or with one computer and more than one turret. For example, if a parallax correction mechanism is installed for each turret, the values of a and S may be adjusted for different control stations as the control of the turret is switched from one control station to another.

For example, if a mechanism is provided for the turret II, the values of oz and S may be set in for either control station 3 or control station 4 depending upon which station was supplying data to the turret.

On the other hand, if a parallax correcting mechanism is installed for each control station, the values of or. and S may be adjusted for different turrets. For example, if a mechanism was installed for control station 3, the values of a and S may be adjusted for turrets 9 and II. Furthermore, the devices for adjusting the values of a and S may be modified to provide more than two adjustments and thereby permit the computation of parallax correction between any number of stations.

It is contemplated that a mechanism similar to that shown in Fig. 3 may be used in conjunction with each of the computers or control stations on an aircraft. Thus, the gun aiming angles determined by the computers at the control stations may be corrected to a suitable turret to position the gun at that turret so it will be directed toward the predicted future position of a target. This mechanism uses only the data ent.

that is supplied by acoinputer, namely, the azimuth, elevation and range data ofthe targets future position relativefto the Computer.

Another mechanismfor'determining the azimuth and elevation parallax correction in accordance with Equations 10 and 11, respectively, is illustrated in Fig. fand will now be described. In this mechanism, shafts I5I, I52 and I53 are positioned by the computer in accordance with the gun azimuth angle, gunjelevation angle and range relative to the computer in a manner simrm to that in which the shafts 2|, 22 and 23- of the mechanism shown in Fig. 3 are positioned.

The shaft I52 drives through gearing I55 and shaft I54 to rotate an elongated pinion I55 in accordance with the gun elevation angle Ed at the computer. The elongated pinion I55 drives a gear I56 that is mounted on a three-dimensional cam I51 to also rotate the cam in accordance with the elevation angle Eo. Cam I51 is translated by a rack I58- that meshes with a pinion I59 on the shaft I53, whereby the cam I51 is translated in accordance with the range D ofthe target. The surface of cam I51 is laid'out in a manner such that a follower IBI ridingthereon is translated in accordance with expression D cos 'EG A secondthree-dimensional cam. L33 is integral with the cam I51, whereby it also is rotated in accordance with the gun elevation Eoand translated in accordance with range R. The surface ofthe cam 563 is laid out in amanner such that follower. I54, riding thereon, will be positioned in accordance with the expression sin E5 Three identical three dimensional car'ns I65 I55 and I51 are mounted on the follower It! and are translated therebyin accordance with the expression a D cosEo.

Additional cams maybe mounted on the'follower I9I1to provide for correcting the data supplied to more turrets, as will subsequently become appar- These three cams I 65 lfit'and I61 are retated in accordance with thegun azimuth angle AG at the computer by an elongated pinion I69. The elongated pinion IE9 is rotated in accordance with AG by shaft I5I which is connected thereto throughsuitable gearing I 1I, I12,'I13 and l l l 'in eluding shafts I15, I'16andl'11. I I

When the mechanism is assembledeachof the cams is set with respect to thepinio'n I69'and the. other cams in accordance with the angle a. for its particular turret, that is, the azimuth angle between thejzero azimuth line and the line connecting the computing or sighting station and the gun turret or station. By settingthe three cams at different angles on with respect to pinion I69, p r'ovisionis made for transmitting data'simultaneously to threeturrets arranged in different fpositions relative to the computing or sighting stations. Assuming the pinion I59 is arranged at zero azimuth, each of thecarns I65; I65 and IE1 will be adjusted angular-1y by an amount corresponding to the angle "a' for their three respective turrets. Thus, by properly selecting'the direction of rotation of the pinion I 59, the Value of the gun azimuth angle AG may be subtracted from the value 'of the angle a. at 'whichthe cams are set, thus obtaining the difference between these two angles, which difference angle 'is the one desired to be used;

. ii? I H 'The carns as, att nd "1151- are translated in aecor-dance with the expression V fDIcos Ed" 7 V and are rotated in accordance with the difference angle (a-As). The surfaces of these cams are such that followers [8 I I82 and -I 83, riding thereon, are translated in accordance with the expression Dcos'E The only differences in the,.trans1ation of these three followers will be the difierencein the angle a for the three turrets, that is, the difference in the angle a by which the three cams I65, I56 and I51 are originally set.

Follower I8I carries a rack- I85 that meshes with a pinion [85 .that rotates ashaft I81 to drive gears I88 and I89. The ratio of the gears I88 and I89 is proportional to the distance S between the computing station and the same gun turret for which the cam I65 was originally'positioned by the angle 0:. Since shaft, I 81 is positioned in accordance with the expression sin (e rie) 1) cos E the shaft I9I will be'positioned by'a similar quantity but multiplied by the distance Sbetween the computing and gun station. Thus, the shaft i9l will be positioned in accordance with-the azimuth parallax correction angle as, as determined by Equation 10. v

The shaft I9 drives this "value of the azimuth parallax correction angle t into 'a differential H2. The other input of differential is driven in accordance with the gun azimuth angle AG at the computer by gearing I53 from the shaft I15, which thereby drives shaft I94, gear I and the other input gear I96 into the differential I92.

Output gear I91 of the differential I92 is thus positioned in'accordance with the sum of the gun azimuth angleAer at'the computing station andethe azimuth parallax correction angle, 6A, which sum is equivalent to the gun azimuth angle A'o at the particular gun turret for which the values of a and S were selected. This gun azimuth angle A'G may be transmitted to the remote turret through suitable dataftransmission and servo. systems. Such systems may be controlled byfazimuth transmitter I98, which is positioned in accordance with the gun azimuth at the selected turret by gear I9 1 which meshes with'a gear-I99 to position the rotor or the transmitter I98 as by shaft 20I.

The addition of the azimuth parallax correction angle and the gun azimuth angle may be accomplished in any well known manner. The use of a differential for this purpose is merely illustrativeof any suitable summing device. For example, the'shafty lalg which is rotated in accordance with the parallax correction angle 6A, might be utilized to rotate the casing of the transmitter I98'and"have the gun azimuth angle shaft I15 drive the'rotor of the transmitter- I98. Thus, the output of the transmitter would represent the sum (AG-:GA) which would be the corrected gun aiming angle A's.

For a second turret, the follower I82 drives pinion 293 and shaft 204 to rotategears 205 and 296, whereby the quantity determined by the follower I82 is multiplied by thevalue of S for the second turret, This product is driven byshaft- 291 to a differential208,: the other input for the third turret.

13 of which is driven in accordance with the gun azimuth AG at the computer in the same manner as that described with respect to differential I92. Thus, output gear 209 of the differential 29B is positioned in accordance with the gun azimuth angle A's at the second turret and drives through gear 2 and shaft 2I2 to position the the cam I63 is positioned in accordance with the expression sin E This follower I64 translates three cams 225, 226 and 221 in accordance with this expression. These cams are rotated an amount corresponding to the difierence angle (cl-AG) in the same manner as that described in connection with cams I65, I66 and I61, the angle a. being adjusted for the three difierent turrets in accordance with the original position of the cams with respect to the elongated pinion I69. Additional cams for additional turrets may also be translated by the follower I64. The three cams 225, 226, and 221 are rotated in accordance with the difference angle by gears 229, 229 and 23I mounted on the three cams, respectively, which mesh with the elongated pinion I69. The cams 225, 226 and 221 are laid out in a manner such that followers 233, 234 and 235 riding on their respective surfaces will be positioned in accordance with the expression sin E cos (w-A the value of a being different for each of the three cams.

This expression is multiplied by the corresponding value of S for each of the three turrets by the ratio of gears 24I to 242; 243 to 244; and 245 to 246. A rack 241 on the follower 243 meshes with 'a pinion 248 which drives through shaft 249 to position the gear 24I. Similarly, racks 25I and 252 on followers 234 and 235; respectively, mesh with pinions 253 and 254 to drive shafts 255 and 256 which in turn are connected to pinions 243 and 245. It will be apparent that shafts 251, 258 and 259 will be positioned in accordance with the elevation parallax correction angle er, as determined by Equation 11 since each of the shafts 249, 255 and 256 has been multiplied by a quantity corresponding to the distance S between the computer and the three respective turrets.

The elevation parallax correction angle era for the first turret is driven into the input of the differential 2-6I, the other input of which is driven by shaft I52, gearing 263, shaft 264, gearing 265, and gearing 266 to drive the gun elevation angle The shaft 2I1 drives the" Be at the computer into the differential 2% i. The output of the differential 261 represents the sum of the gun elevation angle Ea at the computer, and the elevation parallax correction angle eE, which sum is equal to the gun elevation angle E's at the turret. This output acts through gearing 21I and shaft 212 to position the rotor of a. suitable transmitter 213 for controlling data transmission and servo systems to aim the gun in the first turret in accordance with the gun elevation angle E's therefor.

In a similar manner, differential 215 is driven by shaft 258 in accordance with the elevation parallax correction angle es for the second turret, and by a shaft 211 in accordance with the gun elevation angle Ea at the computer. This difierential 215 adds these two angles to obtain the gun elevation angle E's at the second turret and positions the rotor of a suitable transmitter 214 as by gearing 219 and gearing 281 and shaft 282 in accordance with said gun elevation angle at the second turret. Similarly, shaft 259 and a shaft 294 drive the elevation parallax correction angle en for the third turret and the gun elevation angle Ea at the computer into a differential 285, the output gear 296 of which is positioned in accordance with the gun elevation angle E's at the third gun turret. The gear 286 drives through a gear 288 and shaft 289 to position the rotor of a suitable transmitter 29I for actuating suitable transmission and servo systems to control the elevation angle of the gun in the third turret.

The parallax correction mechanism described in connection with Fig. 3 provides a simple mech-- anism for determining the parallax correction angle of a selected turret. The mechanism may i be adjusted by adjusting the values of S and a for this turret. The parallax correction mechanism described in connection with Fig. 5 provides continuous correction data simultaneously for several turrets. The mechanism illustrated in Fig. 5 corrects the computer data for three different turret positions. As has been previously stated, additional cams may be translated by followers I6I and I64. Thus, by providing such additional cams and their auxiliary equipment, the computer data may be corrected for as many turrets as desired. It will be apparent that this mechanism is readily adjustable for different crafts by merely adjusting the relative positions of the cams in accordance with the angle a for the various turrets, and by adjusting the gear ratios in accordance with the various values of S.

For those turrets located on the longitudinal reference line of the craft, the mechanisms are operated in the same manner as for turrets located in the wings. However, the angle on relative to the zero azimuth line becomes 0 or 180. Thus, the mechanism is adjustable for all conditions and corrections for additional turrets may be added to the mechanism as required.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a parallax correction mechanism, means for computing the azimuth parallax correction angle comprising an element for introducing the azimuth angle of a line of aim from one station Fir 2,42%372 r reference line :through said ..one station,.- an relement for introducing the .elevationangl .0f,said line of aimrelative to alreferencehplane including said zero. azimuth line,...an element for introducing the range. of. said .point relative .to said...

.one: station, a .deviceset according. tothe azimuth angle between.saidzeroreference line and a base line fromsaid one station to a remotestation and actuated. by said first .element fordetermining the angular difference between the. azimuth angle of said base line and said azimuth angleaof the line a of aim to said .point, and a mechanismresponsive 1 to said elements andsaid device for computing the azimuth parallax correctionangle forsaidremote station. 2. 'In a parallax correctionsmechanism, means for computing the azimuth-parallax.correction A angle comprising an element for. introducing the azimuth angle-of a line'of aim from-one station to a point measured relativeto. a.zero. azimuth.

- reference line through said one station, an element for introducing the elevationangle-of said line of aim relative to a reference plane including said zero azimuth line; an element for introducing the range-of said poi-nt relative ztogsaid one -station, a device-set according-.tmthe azimuth angle i. between saidzero reference. line and a base line from said-one station to aremotestaing meansfor computing the elevation parallax correction angle, said -meansincluding an element for introducingthe azimuth angle of a line of aim from onestation to apoint measured relative to a zeroazimuth' reference line-through said one station, an element for introducing the elevation angle of said lineof aimv relative toa 7 reference plane including said zero azimuth line, an element for introducing the range of said point relative to said one statiom a device-set according to the azimuth I angle between said zero reference line and a base line .fromsaid one station to a remote station and actuated by said first element for determining the angulardif- 'ferencebetween the azimuth angle of...said base line and.- said azimuthangle of theline of aim to said'point, and a-mechanism actuated by. said elements and said device -for computing the elevation parallax correction angles forsaid remote station.

4. An azimuth parallaxcorrection mechanism comprising a first device actuatediaccording to the range of a point. relative -.to a :first; station and the elevation angle. of a lineof, aim from said first station to said pointameasuredvrelative to a referenceplane includingsaidfirst stationfor providing a measure of theproduct of said .rangeand a ..cosine function .of. 'said; elevation angle, a second device actuated. .by. said zfirst device and according to the angular. difference between the azimuth angle. f thetzline .ofr aim I measured relative to a zeroaa zimuthlreference line in -said--reference plane. and; the. azimuth angle of a baseflline joining Sa,ld'.'ifi1Ststation and a remote station. also. measured.-.relative to said zero reference.- line for .providing a; measure 1 6 ofi the quotientof. a...sine:..function.:of.said' dif eference angle. divided. .by. saidproduct, andmechanismhactuatedbysaidsecond device for. multiplying saidi quotient bythe distance ..betw.een said stations for computing the azimuth parallax correction. angle corresponding to the difference ;-.between said azimuthv angle of the line ofaim ..from said point. to said ,first station and the azimuth angle of a.line from said. point. tosaid remote station.

5... An elevation .parallax. correction mechanism comprising, a first device. actuated. accordinglgto the. range of appoint relative to afirst station and.the elevation angle of a line of aim .from said, first station .to said .point.measured relative 1 to a reference plane includingsaidfirst station .Hforo providing. a measure .of the..quotient..of a sine function :of said -.elevation angle divided .by .saidrange, a second device actuated by saidifirst devicehand according to the. angular difference .betweenthe azimuthangle of the line of .aim measured relative. to a zero azimuth reference line in saidmeference plane and theazimuth angle of abase line joining said first stationand a remote station for. providing a measure iof lthe product of a cosine function of said difference angle multiplied by said quotient, and mechanism actuated by said seconddevice for multiplying said product by the distances between said stations, to compute the elevation parallax correcqtion tangle corresponding to the diiferencebetween the said elevation angle of the line of aim fromsaid point to said first station and the elevation angle ofa line from said point to, said .remote station. 7

1 6.1.A parallaxcorrection mechanism comprising a range. membersettable according to the range of. a point relative to afirst station, an elevation member settableraccording to the elevation angle of a line of aim from said first station to said "point measured relative to a reference. plane includingsaidfirst station, afirst device actu- .1 ated by said members forproviding a measure .of theproduct of said range and a cosine function of said elevation-angle, a seconddevice actuated byosaid members. for providing a measure of. the quotient of a sincefunctionof said angle divided by said range, an -azirnuth memberrsettable according to the azimuth angular position of said line of. aim measured relative to a zero reference line including said first station, ,a third devicev actuated bysaid first deviceand said azimuth member according to .the .angular difference between the azimuthangle of the line between said first,station, and the. said remote station measured relative 'tolsaidzero reference lineand said; azimuth angle of said line of aim forproviding a measure ofthe quotient offla sinefunction of said-difference ,angle. divided by said product mechanism actuated by-fsaid l third device for multiplying said quotient by the ,distance between said stations. to compute the azimuth parallax correction angle of said. point i with respect to said stations, a'fourth devicel'actuatedby said second deviceand said azimuth gmemberaccording- "to said difference, anglemfor providing a measure of the product. of said q'u oytient ,multiplied by. aQcosi nefunction .of said difference angle and mechanism actuated by said fourth device for multiplyingsaidproduct bythe distance between. said stations. to compute the elevation parallax correction.angle,of. .saidpqint with respect to said two-stations. I

- 7;. An azimuth parallax correction mechan ism comprisin an azimuthelement tor... providing a measure of the azimuth angular position of a line of aim from a point to a first station measured relative to a zero azimuth reference line including said first station, an elevation element for providing a measure of the elevation angle of said line of aim measured relative to a reference plane including said reference line, a range element for providing a measure of the range of said point with respect to said first station, computing means actuated by said three elements for computing the quotient of a sine function of said azimuth angle divided by the product of a cosine function of said elevation angle and the range of said point, gear means driven by the output of the computing means having a predetermined ratio proportional to the distance between said first and a second station for multiplying said quotient by said distance to provide a measure of the azimuth parallax correction angle between said stations, and a clutch controlling the gear means operable to change said gear ratio to a different predetermined ratio proportional to the distance between said first station and a third station, to adapt the mechanism at will for use with the latter station and said first station.

8. An elevation parallax correction mechanism comprising an azimuth element for providing a measure of the azimuth angular position of a line or" aim from a point to a first station measured relative to a zero azimuth reference line including said first station, an elevation element providing a measure of the elevation angle of said line of aim measured relative to a reference plane including said reference line, a range element for providing a measure of the range of said point with respect to said first station, computing means actuated by said three elements for computing the product of the sine of said elevation angle and the cosine of said azimuth angle divided by the range of said point, gear means driven from the output of the computing means having a ratio proportional to the distance between said first and a second station for multiplying said output by said distance to provide a measure of the elevation parallax correction between said stations, a clutch controlling the gear means operable to change said gear ratio to a different predetermined gear ratio proportional to the distance" between said first station and a third station, whereby the mechanism may be adapted by the operation of the clutch for use with the latter station and said first station.

9. An azimuth parallax correction mechanism comprising an azimuth element for providing a measure of the difference angle between the azimuth angular position of a line of aim from a point to a first station measured relative to a zero reference line including said first station and the azimuth angular position of a line joining said first station and a second station measured relative to said zero reference line, an elevation element providing a measure of the elevation angle of said line of aim measured relative to a reference plane including said reference line, a range element for providing a measure of the range of said point with respect to said first station, computing means actuated by said three elements for computing the quotient of a sine function of said difference angle divided by the product of a cosine function of said elevation angle and the range of said point, a member settable according to the distance between said stations, and multiplying means actuated by said computing means and said member for multiplying said quotient by said distance to provide a measure of the azimuth parallax correction angle between said stations.

10. An elevation parallax correction mechanism comprising an azimuth element for providing a measure of the difference angle between the azimuth angular position of a line of aim from a point to a first station measured relative to a zero reference line including said first station and the azimuth angular position of a line joining said first station and a second station measured relative to said zero reference line, an elevation element providing a measure of the elevation angle of said line of aim measured relative to a reference plane including said reference line, a range element for providing a measure of the range of said point with respect to said first station, computing means actuated by said three elements for computing the product of a cosine function of said difference angle multiplied by a sine function of said elevation angle, divided by the range of said point, a, member settable according to the distance between said stations and multiplying means actuated by said computing means and said member for multiplying said product by said distance to provide a measure of the elevation parallax correction angle between said stations.

RICHARD C. KNOWLES. HERBERT HARRIS, JR.

REFERENCES CITED Country Date Italy Sept, 14, 1938 Number 

